This invention relates to a coupling involving two components abutting one on the other under preload.
With separable joints, such couplings typically are unions for crimped joints, bayonet signs for bayonet joints, or clamps for flanged connections. These couplings are embarassed by a disadvantage in that they require means to be provided on the components for clamping the components to each other, such as threads, bayonet latches or conical flanges. These means disadvantageously economize neither space nor weight.
With inseparable interlocking joints, use is made of, e.g., die or pressing clamps. These couplings require less installation space then separable couplings, but they disadvantageously assume that the components to be joined together permit of cold or hot forming.
Inseparable brazed or welded joints require the least bulk and weight, but they disadvantageously can be used only with weldable materials.
In a broad aspect of the present invention a coupling of the generic description given above is provided to achieve an inseparable, heat-resistant connection between two components of materials which cannot be welded or brazed together and cannot be cold or hot formed, where the coupling can be adapted to suit differing component sections and is designed to economize space and weight.
It is a particular object of the present invention to provide a coupling in which a coupling sleeve overlapping two components in the area of the mating surface lodges against a first component via an abutment and in which the preload is transmitted to the second component through a welded joint.
In this arrangement of the present invention the weld between the coupling sleeve and one of the components to be connected, or between two coupling sleeves, will shrink when the weld is made and cooled, so that a preload is achieved between the components in the joint to clamp them together in a heat-resistant and inseparable connection.
To enhance the preload between the two components, the components and the coupling sleeve can be assembled together under additional preload in a clamping device, such as a vise, and then welded together under this preload.
The arrangement of the present invention thus avoids disadvantages involved in the state of the art and affords an advantage over separable joints in that functional surfaces, such as mating, faying or bearing surfaces of the abutment can be adapted to suit the cross-sections of the components to be joined together and so save space and weight.
In a first embodiment of the present invention the weld joint is arranged directly between the coupling sleeve and the second component, which assumes that the coupling sleeve and the second component are made of materials that can be welded together.
In a second embodiment of the present invention the weld joint is arranged between the coupling sleeve and a second coupling sleeve, where the preload is transmitted to the second component through an abutment on the second coupling sleeve. This arrangement advantageously permits components to be joined together when their materials cannot be welded to the material of the coupling sleeve.
In an especially advantageous aspect of the present invention the coupling sleeve consists of a material that has a higher coefficient of thermal expansion than the material of one or both of the components, preferably so when the coupling sleeve is made of metal and one or both of the components of a ceramic material. Since the coupling sleeve will axially shrink more than one or both of the components, an additional preload is achieved that superimposes on the shrinkage of the weld when the components cool down.
This effect is advantageously enhanced when the length of the coupling sleeve is made 3 to 30 times, preferably 5 to 15 times its wall thickness.
Separable couplings require circular or partially circular functional surfaces, so that on components of noncircular cross-section, bulky flanges must be provided as cross-sectional transitions. In a further advantageous aspect of the present invention, therefore, the form of the functional surfaces of the coupling sleeve is adapted to suit the cross-sections of the two components.
The coupling of the present invention is especially well-suited for tubular components of round, oval or angular section.
If the invention is utilized in gas-wetted systems it will be advantageous to give the mating surface an axially aligned radial spigot plus a gas-tight, conical or spheroidal sealing face.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.